Imitation is the sincerest form of flattery, right? It appears that Bethesda and Behaviour Interactive have had a falling-out. Bethesda is suing Westworld mobile game publisher Warner Bros. and developer Behaviour Interactive for mimicking Fallout Shelter.

Fallout Shelter is a free-to-play mobile game that was developed by Bethesda Game Studios and Behaviour Interactive. Players must build and manage their own fallout shelter or “Vault”. Fallout Shelter was initially released for iOS in June 2015 and is now also available on Android devices, Windows, Xbox One, Playstation 4, and Nintendo Switch.

The game earned over $5.1 million USD within the first two weeks of its release. Behaviour Interactive, one of the largest independent Canadian video game developers, has developed only one other mobile game between the release of Fallout Shelter and Westworld. Bethesda believes that Warner Bros. coveted their success and induced Behaviour to divulge Bethesda’s trade secrets.

Bethesda is specifically suing the Westworld mobile game creators for copyright infringement, breach of contract, inducement for breach of contract, the misappropriation of trade secrets, and deceptive business practices. They insist that “Behaviour breached its contract with Bethesda and utilized its restricted access to Bethesda’s intellectual property, including Bethesda’s copyrighted code, trade secrets, and other rights, to compress its development timeline, reduce costs, and quickly bring the Westworld mobile game to market…” Warner Bros. is included in the lawsuit because they reportedly had a “direct financial interest” in copying Bethesda’s game.

The lawsuit argues that the Westworld mobile game is a “blatant rip-off” of Fallout Shelter. They contend that Westworld incorporates similar gameplay experiences, features, art style, and animations. They believe that the creators simply “made cosmetic modifications for Westworld’s ‘western’ theme.”

Bethesda argues that the most obvious evidence of copyright infringement can be found in the game’s coding. A bug allows for the demo version of Westworld to appear out of focus. This bug also appeared in Fallout Shelter, but was later fixed.

Bethesda hopes for a jury trial and for compensation to recover damages. Warner Bros. and Behaviour Interactive have not yet commented on the lawsuit. Westworld was released yesterday and is available for Android and iOS.